Top Document: Satellite Imagery FAQ - 3/5 Previous Document: Do I need geocoded imagery? Next Document: What is a Sounding Instrument? See reader questions & answers on this topic! - Help others by sharing your knowledge Imaging Instruments How do Remote Sensing Instruments work? If you put a camera into orbit and point it at the Earth, you will get images. If it is a digital camera, you will get digital images. Of course, this simplistic view is not the whole story. Digital images comprise two-dimensional arrays of pixels. Each pixel is a sensor's measurement of the albedo (brightness) of some point or small area of the Earth's surface (or atmosphere, in the case of clouds). Hence a two-dimensional array of sensors will yield a two-dimensional image. However, this design philosophy presents practical problems: a useful image size of 1000x1000 pixels requires an array of one million sensors, along with the corresponding circuitry and power supply, in an environment far from repair and maintenence! Such devices (charge coupled deices) do exist, and are essentially similar to analogue film cameras. However, the more usual approach for Earth Observation is the use of tracking instruments: Tracking Instruments 1. A tracking instrument may use a one-dimensional array of sensors - one thousand rather than one million - perpendicular to the direction of the satellite's motion. Such instruments, commonly known as pushbroom sensors, instantaneously view a line. A two-dimensional image is generated by the satellite's movement, as each line is offset from its predecessor. If the sampling frequency is equal to the satellite's velocity divided by the sensor's field of view, lines scanned will be contiguous and non-overlapping (although this is of course not an essential property). _btw, would the above be better expressed in some ASCII representation of mathematical notation?_ 2. Another approach is to use just a single sensor. It is now not sufficient to use the satellite's motion to generate an image: cross-track scanning must also be synthesised. This is accomplished by means of a rotating mirror, imaging a line perpendicular to the satellite motion. These are known as scanning instruments. This is somewhat analagous to the synthesis of television pictures by CRT, although the rotating mirror is a mechanical (as opposed to electromagnetic) device. As the sensor now requires a large number of samples per line, the sampling frequency necessary for unbroken coverage is proportionally increased, to the extent that it becomes a design constraint. A typical Earth Observation satellite moves at about 6.5 Km/sec, so a 100m footprint requires 65 lines per second, and higher resolution imagery proportionally more. This in turn implies a sampling rate of 65,000 per second for a 1000-pixel swath. This may be alleviated by scanning several lines simultaneously. Either design of scanning instrument may have colour vision (ie be sensitive to more wavelength of light) by using multiple sensors in parallel, each responding to one of the wavelengths required. List of Imaging Spectrometers http://www.geo.unizh.ch/~schaep/research/apex/is_list.html User Contributions:Comment about this article, ask questions, or add new information about this topic:Top Document: Satellite Imagery FAQ - 3/5 Previous Document: Do I need geocoded imagery? Next Document: What is a Sounding Instrument? Part1 - Part2 - Part3 - Part4 - Part5 - Single Page [ Usenet FAQs | Web FAQs | Documents | RFC Index ] Send corrections/additions to the FAQ Maintainer: satfaq@pobox.com
Last Update March 27 2014 @ 02:12 PM
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Russians who want to impress their social media followers can now rent huge bouquets of flowers for just long enough to snap an Instagram worthy photo, It's revealed.
Pop up services are advertising on social networks in planning for International Women's Day on 8 March, A public holiday in Russia when women are in the past feted with flowers and other gifts. They're offering 10 minutes with an enormous bouquet sufficient time to perfect the best angle and pose before the courier takes it back, The TJournal news blog reports. One account offers women a fleeting visit from 101 roses for 700 roubles ($12; 10).
Posting selfies with huge bouquets seemingly sent by a boyfriend or secret admirer has been a trend among Russian Instagram and VKontakte social network users for quite a while.
The 360 TV website contacted the master of one flower rental Instagram account, [url=https://charmdatescamreviews.wordpress.com/tag/hot-russian-women/]russian sexy girls[/url] Who insisted his service was real and had received many asks. He says the 10 minutes can be drawn out a little, But not consistently. "the most important thing to avoid is: 'I'm obtaining put some make up on and tidy up' and all that', according to him.
Another account that 360 TV contacted ended up being a joke set up to mock the new trend, And there was plenty of ridicule from Russians placing comments online. "the secret of a mysterious bunch of flowers from a stranger has been EXPOSED, Writes an individual on Twitter. "might be quintessence of modern values, Says an Instagram surfer, Who suggests similar service aimed at men: "A Rolex download, Two iPhones shared and a selfie taken in a Moscow office with a panoramic view.